Particular attention has been paid to the FeBR base magnets as novel high-performance permanent magnets using rare earth elements (R) represented by Nd, Pr and the like. As already disclosed in Japanese Patent Kokai-Publication No. 59-46008 filed by the present applicant company, the FeBR base magnets have properties comparable to those of the prior art high-performance magnets SmCO, and are advantageous in that scarece and expensive Sm is not necessarily used as the essential ingredient. In particular, since Nd has been considered to be a component of substantially useless, it is very advantageous that Nd can be used as the main component.
However, since the FeBR magnet alloys have a relatively low Curie temperature that is around 300.degree. C., there is a fear that their stability at temperatures higher than room temperature may be insufficient. It has been proposed to improve the stability of the FeBR magnet alloys with respect to temperature by substituting Co for a part of Fe to form FeCoBR magnet alloys (see Japanese Patent Kokai-Publication No. 59-64733).